Signal transmission method performed by relay station in wireless communication system and apparatus thereof

ABSTRACT

Disclosed is a signal transmission method performed by a relay station in a wireless communication system. The method comprises the steps of: arranging guard time within at least one symbol period in a subframe which is configured with multiple symbol periods in a time domain; and transmitting a control signal or data to a base station by using symbol periods except for the symbol periods which include the guard time in the subframe. The guard time is equal to or shorter than one symbol period. The structure in which the control signal or the data is arranged in each symbol period of the subframe is determined on the basis of the number of symbol periods except for the symbol periods which include the guard time.

TECHNICAL FIELD

The present invention relates to wireless communication and, moreparticularly, to a method and apparatus in which a relay stationtransmits a signal in a wireless communication system.

BACKGROUND ART

In the ITU-R (International Telecommunication Union Radio communicationsector), a standardization work for IMT (International MobileTelecommunication)-Advanced (i.e., the next-generation mobilecommunication system after the third generation) is in progress.IMT-Advanced sets its goal to support IP (Internet Protocol)-basedmultimedia service at the data transfer rate of 1 Gbps in stop andslow-speed moving states and of 100 Mbps in a fast-speed moving state.

One of the powerful candidates as a system standard to satisfy therequirements of IMT-Advanced is LTE-A (Long Term Evolution-Advanced) of3GPP (3rd Generation Partnership Project). LTE-A is an improved versionof 3GPP LTE (hereinafter referred to as ‘LTE’). LTE is part of E-UMTS(Evolved-UMTS) using an E-UTRAN (Evolved-Universal Terrestrial RadioAccess Network). The LTE adopts OFDMA (Orthogonal Frequency DivisionMultiple Access) in downlink and SC-FDMA (Single Carrier-FrequencyDivision Multiple Access) in uplink.

In the LTE-A, consideration is taken of a relay station to be includedin a wireless communication system. The relay station functions toextend the cell coverage and improve transmission performance. A basestation can have an advantage of extending the cell coverage byservicing mobile stations, located in the cell coverage thereof, throughrelay stations. Further, since the relay stations improve transmissionreliability between the base station and the mobile stations, thetransmission capacity can be increased. A relay station may be utilizedin the case in which a mobile station is located in a shadow regionalthough it is within the coverage of a base station.

A relay station commonly divides subframes into a reception subframe forreceiving a signal from a mobile station connected thereto and atransmission subframe for sending a signal to a base station in order toprevent self-interference. Here, guard time needs to be placed in thereception subframe or the transmission subframe of a signal. The guardtime is used for stabilization and the prevention of interferenceaccording to the transmission/reception switching of a signal in a relaystation. If the guard time is included in the transmission subframe,available time resources that the relay station can transmit a signal tothe base station are reduced.

Meanwhile, in a wireless communication system environment, fading isgenerated owing to multi-path time delay. A process of restoring atransmission signal by compensating for the distortion of the signal,generated owing to an abrupt change in the environment due to fading, iscalled channel estimation. In general, channel estimation is performedusing a reference signal (RS) known to both a receiver and atransmitter. A relay station can also transmit the reference signal to abase station.

There is a need for a signal transmission method with considerationtaken of the fact that, if a relay station transmits a signal to a basestation, available time resources are gradually reduced in a linkbetween the relay station and the base station owing to the guard time.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method and anapparatus in which a relay station transmits a signal in a wirelesscommunication system.

Technical Solution

A method of a relay station transmitting a signal in a wirelesscommunication system in a wireless communication system includes thesteps of placing guard time within at least one symbol period in asubframe including a plurality of symbol periods in the time domain andtransmitting a control signal or data to a base station using symbolperiods other than the symbol period, including the guard time, in thesubframe, wherein the guard time is equal to or shorter than one symbolperiod, and a structure in which the control signal or the data isplaced in each of the symbol periods of the subframe is determined basedon the number of symbol periods other than the symbol period includingthe guard time.

Advantageous Effects

A relay station can transmit a signal through radio resources allocatedthereto by taking guard time into account. Interference between asounding reference signal transmitted by a mobile station and a soundingreference signal transmitted by a relay station is reduced.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows a wireless communication system using relay stations.

FIG. 3 shows the structure of a radio frame in 3GPP LTE.

FIG. 4 shows an example of a resource grid for one downlink slot.

FIG. 5 shows the structure of a downlink subframe.

FIG. 6 shows the structure of an uplink subframe.

FIG. 7 is a diagram showing a timing relationship between subframes onwhich a base station receives a signal from a macro mobile station or arelay station.

FIG. 8 shows an example of the structure of a non-shifting subframe ifguard time is placed in the first symbol and the last symbol of thenon-shifting subframe.

FIG. 9 shows another example of the structure of a non-shifting subframeif guard time is placed only in the first symbol of the non-shiftingsubframe.

FIG. 10 shows an example of the structure of a shifting subframe ifguard time is placed in the first symbol and the last symbol of theshifting subframe.

FIG. 11 shows another example of the structure of a shifting subframe ifguard time is placed only in the first symbol of the shifting subframe.

FIG. 12 shows examples of shortened R-PUCCH formats in a non-shiftingsubframe.

FIG. 13 shows another example of shortened R-PUCCH formats in anon-shifting subframe.

FIG. 14 shows examples of shortened R-PUCCH formats in a shiftingsubframe.

FIG. 15 shows another example of shortened R-PUCCH formats in a shiftingsubframe.

FIG. 16 shows yet another example of shortened R-PUCCH formats in ashifting subframe.

FIG. 17 shows examples of shortened R-PUCCH formats if guard time isplaced only in the first slot of a subframe in a shifting subframe.

FIG. 18 shows another example of shortened R-PUCCH formats if guard timeis placed only in the first slot of a subframe in a shifting subframe.

FIG. 19 shows yet another example of shortened R-PUCCH formats if guardtime is placed only in the first slot of a subframe in a shiftingsubframe.

FIG. 20 shows an example in which radio resources are allocated in orderto transmit an R-SRS in a non-shifting subframe.

FIG. 21 shows another example in which radio resources are allocated inorder to transmit an R-SRS in a non-shifting subframe.

FIG. 22 shows yet another example in which radio resources are allocatedin order to transmit an R-SRS in a non-shifting subframe.

FIG. 23 shows examples of shortened R-PUCCH formats if an SRS and anR-SRS are transmitted in a non-shifting subframe.

FIG. 24 shows another example of shortened R-PUCCH formats if an SRS andan R-SRS are transmitted in a non-shifting subframe.

FIG. 25 shows examples of shortened R-PUCCH formats having symmetricstructures on the basis of a slot boundary if only an SRS is transmittedin a non-shifting subframe.

FIG. 26 shows examples of shortened R-PUCCH formats having symmetricstructures on the basis of a slot boundary, if an SRS and an R-SRS aretransmitted in a non-shifting subframe.

FIG. 27 shows an example in which an orthogonal sequence is applied to ashortened R-PUCCH format having a symmetric structure.

FIG. 28 shows an example of a subframe structure if an R-SRS istransmitted in a shifting subframe.

FIG. 29 shows another example of a subframe structure if an R-SRS istransmitted in a shifting subframe.

FIG. 30 shows an example of a subframe structure if guard time is placedonly in the first symbol and an R-SRS is transmitted in a non-shiftingsubframe.

FIG. 31 shows another example of a subframe structure if guard time isplaced only in the first symbol and an R-SRS is transmitted in anon-shifting subframe.

FIG. 32 shows yet another example of a subframe structure if guard timeis placed only in the first symbol and an R-SRS is transmitted in anon-shifting subframe.

FIGS. 33 and 34 show still another example of subframe structures ifguard time is placed only in the first symbol and an R-SRS istransmitted in a non-shifting subframe.

FIG. 35 shows a method of multiplexing an R-SRS and an SRS in thesubframe structures of FIGS. 33 and 34.

FIG. 36 shows radio resources generated when the placement of guard timebetween two consecutive subframes is unnecessary, in relation to anon-shifting subframe and a shifting subframe.

FIG. 37 shows a subframe structure in which an R-PUCCH and an R-PUSCHare subjected to TDM if guard time is placed in the first symbol and thelast symbol of a non-shifting subframe.

FIG. 38 shows radio resources remained in the first symbol and the lastsymbol of a non-shifting subframe if guard time is placed in the firstsymbol and the last symbol.

FIG. 39 shows a subframe structure in which an R-PUCCH and an R-PUSCHare subjected to TDM if guard time is placed in the first symbol and thelast symbol of a shifting subframe.

FIG. 40 shows a special resource region if guard time is placed in thefirst symbol and the last symbol of a shifting subframe. The guard timemay be, for example, a ½ symbol.

FIG. 41 shows a subframe structure in which an R-PUCCH and an R-PUSCHare subjected to TDM if guard time is placed only in the first symbol ofa shifting subframe.

FIG. 42 shows an operation of a relay station transmitting and receivingsignals in a series of shifting subframes in each of which the guardtime is placed only in a first ½ symbol.

FIG. 43 shows an example in which an R-SRS is transmitted if guard timeis placed in the first symbol and the last symbol of a non-shiftingsubframe.

FIG. 44 shows another example in which an R-SRS is transmitted if guardtime is placed in the first symbol and the last symbol of a non-shiftingsubframe.

FIG. 45 shows yet another example in which an R-SRS is transmitted ifguard time is placed in the first symbol and the last symbol of anon-shifting subframe.

FIG. 46 shows an example in which an R-SRS is transmitted if guard timeis placed in the first symbol and the last symbol of a shiftingsubframe.

FIG. 47 shows an example in which an R-SRS is transmitted in the entiresystem band if guard time is placed in the first symbol and the lastsymbol of a shifting subframe.

FIG. 48 shows an example in which an R-SRS is transmitted if guard timeis placed only in the first symbol of a shifting subframe.

FIG. 49 shows another example in which an R-SRS is transmitted if guardtime is placed only in the first symbol of a shifting subframe.

FIG. 50 shows yet another example in which an R-SRS is transmitted ifguard time is placed only in the first symbol of a shifting subframe.

FIG. 51 shows still another example in which an R-SRS is transmitted ifguard time is placed only in the first symbol of a shifting subframe.

FIG. 52 shows further another example in which an R-SRS is transmittedif guard time is placed only in the first symbol of a shifting subframe.

FIG. 53 is a block diagram showing a wireless communication system inwhich the embodiments of the present invention are implemented.

MODE FOR INVENTION

The following technologies may be used in a variety of wirelesscommunication systems, such as CDMA (Code Division Multiple Access),FDMA (Frequency Division Multiple Access), TDMA (Time Division MultipleAccess), OFDMA (Orthogonal Frequency Division Multiple Access), andSC-FDMA (Single Carrier Frequency Division Multiple Access). CDMA may beimplemented using radio technologies, such as UTRA (UniversalTerrestrial Radio Access) or CDMA2000. TDMA may be implemented usingradio technologies, such as GSM (Global System for Mobilecommunications)/GPRS (General Packet Radio Service)/EDGE (Enhanced DataRates for GSM Evolution). OFDMA may be implemented using radiotechnologies, such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). IEEE 802.16m is an evolution of IEEE802.16e, and it provides backward compatibility with systems based onIEEE 802.16e. UTRA is part of a UMTS (Universal MobileTelecommunications System). 3GPP (3^(rd) Generation Partnership Project)LTE (Long Term Evolution) is part of E-UMTS (Evolved UMTS) using E-UTRA(Evolved-UMTS Terrestrial Radio Access). 3GPP LTE adopts OFDMA indownlink and adopts SC-FDMA in uplink. LTE-A (Advanced) is an evolutionof 3GPP LET. In order to clarify a description, LTE/LTE-A are chieflydescribed, but the technical spirit of the present invention is notlimited thereto

FIG. 1 shows a wireless communication system.

The wireless communication system 10 includes at least one Base Station(BS) 11. The BSs 11 provide communication services to respectivegeographical areas (in general, called cells) 15 a, 15 b, and 15 c. Thecell may be divided into a plurality of areas (called sectors). UserEquipment (UE) 12 may be fixed and mobile and also referred to asanother terminology, such as an MS (Mobile Station), an MT (MobileTerminal), a UT (User Terminal), an SS (Subscriber Station), a wirelessdevice), PDA (Personal Digital Assistant), a wireless modem, or ahandheld device. The BS 11 commonly refers to a fixed station whichcommunicates with the user stations 12, and it can also be referred toas another terminology, such as an eNB (evolved-NodeB), a BTS (BaseTransceiver System), or an access point. Hereinafter, downlink refers tocommunication from the BS 11 to the user equipment 12, and uplink refersto communication from the user equipment 12 to the BS 11.

FIG. 2 shows a wireless communication system using relay stations.

In uplink transmission, a source station may be an MS, and a destinationstation may be a BS. In downlink transmission, a source station may be aBS, and a destination station may be an MS. A relay station may be anMS, and an additional relay station may be deployed. A BS may performfunctions, such as connectivity, management, control, and resourceallocation between a relay station and an MS.

Referring to FIG. 2, a destination station 20 communicates with a sourcestation 30 via a relay station 25. In uplink transmission, the sourcestation 30 transmits uplink data to the destination station 20 and therelay station 25. The relay station 25 retransmits the received data.Furthermore, the destination station 20 communicates with a sourcestation 31 via relay stations 26 and 27. In uplink transmission, thesource station 31 transmits uplink data to the destination station 20and the relay stations 26 and 27. The relay stations 26 and 27retransmit the received data sequentially or at the same time.

Although one destination station 20, the three relay stations 25, 26,and 27, and the two source stations 30 and 31 are illustrated, thepresent invention is not limited to the above example. The number ofdestination stations, relay stations, and source stations included inthe wireless communication system is not limited. Any method, such asAmplify and Forward (AF) and Decode and Forward (DF), may be used as arelay method used in the relay stations 25, 26, and 27, but thetechnical spirit of the present invention is not limited thereto.

Hereinafter, a link between a relay station and a BS is referred to as abackhaul link, and a link between a relay station and UE is referred toas an access link. Communication from a relay station to a BS isreferred to as backhaul uplink (hereinafter referred to as backhaul UL),and communication from a BS to a relay station is referred to asbackhaul downlink (hereinafter referred to as backhaul DL).Communication from UE to a relay station is referred to as access uplink(access UL), and communication from a relay station to UE is referred toas access downlink (access DL). UE directly communicating with a BS isreferred to as a macro UE (Ma-UE), and UE communicating with a relaystation is referred to as a relay UE (Re-UE).

FIG. 3 shows the structure of a radio frame in 3GPP LTE. For thestructure, reference may be made to section 5 of 3GPP (3rd GenerationPartnership Project) TS 36.211 V8.2.0 (2008-03) “Technical SpecificationGroup Radio Access Network; Evolved Universal Terrestrial Radio Access(E-UTRA); Physical channels and modulation (Release 8)”.

Referring to FIG. 3, the radio frame includes 10 subframes. One subframeincludes two slots. The slots within the radio frame are assigned slotnumbers or slot indices from #0 to #19. The time that it takes totransmit one subframe is referred to as a TTI (Transmission TimeInterval). The TTI may be said to be a scheduling unit for datatransmission. For example, the length of one radio frame may be 10 ms,the length of one subframe may be 1 ms, and the length of one slot maybe 0.5 ms.

One slot includes a plurality of unit times in the time domain andincludes a plurality of subcarriers in the frequency domain. The unittime is hereinafter called a symbol period or simply a symbol, for thesake of convenience. That is, the symbol may be a specific interval inthe time domain. The symbol may be called another terminology accordingto a multiple access scheme. For example, an OFDM symbol is used torepresent one symbol period because 3GPP LTE uses OFDMA in downlink. IfSC-FDMA is used as an uplink multiple access scheme, it may be called anSC-FDMA symbol. 3GPP LTE is defined to include 7 OFDM symbols in oneslot in a normal Cyclic Prefix (CP) and 6 OFDM symbols in one slot in anextended CP.

FIG. 4 shows an example of a resource grid for one downlink slot.

The downlink slot includes a plurality of OFDM symbols in the timedomain and an N_(RB) number of Resource Blocks (RBs) in the frequencydomain. The number of resource blocks N_(RB) included in a downlink slotdepends on a downlink transmission bandwidth configured in a cell. Forexample, in an LTE system, the number of resource blocks N_(RB) may beany one of 60 to 110. One resource block includes a plurality ofsubcarriers in the frequency domain. An uplink slot may also have thesame structure as the downlink slot.

Each element on the resource grid is referred to as a resource element(RE). The RE on the resource grid may be identified by an index pair(k,l) within a slot. Here, k (where k=0, . . . , N_(RB)×12−1) is asubcarrier index within the frequency domain, and l (where l=0, . . . ,6) is an OFDM symbol index within the time domain.

It is hereinafter illustrated that one resource block includes 7 OFDMsymbols in the time domain and 12 subcarrier in the frequency domain,resulting in 7×12 REs. However, the number of OFDM symbols and thenumber of subcarriers within a resource block are not limited thereto.The number of OFDM symbols and the number of subcarriers may be changedin various ways according to the length of a Cyclic Prefix (CP),frequency spacing, etc.

FIG. 5 shows the structure of a downlink subframe.

The downlink subframe includes 2 slots in the time domain. Each of theslots includes 7 OFDM symbols in a normal CP. A maximum of the first 3OFDM symbols of the first slot within the subframe correspond to acontrol region to which control channels are allocated, and theremaining OFDM symbols correspond to a data region to which PDSCHs(Physical Downlink Shared Channels) are allocated. Downlink controlchannels used in 3GPP LTE include a PCFICH (Physical Control FormatIndicator Channel), a PDCCH (Physical Downlink Control Channel), a PHICH(Physical Hybrid-ARQ Indicator Channel), and so on. The PCFICHtransmitted in the first OFDM symbol of a subframe carries informationabout the number of OFDM symbols (i.e., the size of a control region)which is used to transmit control channels within a subframe. The PHICHcarries an ACK/NACK signal for an HARQ (uplink Hybrid Automatic RepeatRequest). That is, an ACK/NACK signal, transmitted by a BS in responseto uplink data transmitted by UE, is transmitted on the PHICH. Controlinformation transmitted through the PDCCH is also referred to asdownlink control information (DCI). The DCI indicates uplink or downlinkscheduling information and an uplink transmission power control commandfor certain UE groups.

FIG. 6 shows the structure of an uplink subframe.

The uplink subframe may be divided into a control region and a dataregion in the frequency domain. A PUCCH (Physical Uplink ControlChannel) for transmitting uplink control information is allocated to thecontrol region.

The PUCCH may support a multi-format. That is, the PUCCH may be used totransmit uplink control information having different numbers of bits persubframe according to a modulation scheme. For example, if BPSK (BinaryPhase Shift Keying) is used (PUCCH format 1a), the uplink controlinformation of 1 bit may be transmitted on the PUCCH. If QPSK(Quadrature Phase Shift Keying) is used (PUCCH format 1b), the uplinkcontrol information of 2 bits may be transmitted on the PUCCH. The PUCCHformat may include a format 1, a format 2, a format 2a, a format 2b, andso on (reference may be made to section 5.4 of 3GPP TS 36.211 V8.2.0(2008-03) “Technical Specification Group Radio Access Network; EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation (Release 8)”).

After RB pairs are configured within a subframe, the PUCCHs of one UEare allocated. RBs included in the RB pair occupy different subcarriersof each slot. It is said that the frequency of the RB pair allocated tothe PUCCH has been frequency-hopped in the slot boundary.

A PUSCH (Physical Uplink Shared Channel) for sending data is allocatedto the data region. In 3GPP LTE, in order to maintain the characteristicof a single carrier, UE does not transmit the PUCCH and the PUSCH at thesame time.

The above uplink subframe structure is applied between a BS and UE.However, if the uplink subframe structure is applied to backhaul ULlikewise, a problem may arise. A relay station receives a signal from arelay UE and transmits the signal to a BS. Alternatively, a relaystation receives a signal from a BS and transmits the signal to a relayUE. That is, the relay station performs switching for the transmissionand reception of signals in the backhaul link and the access link. Here,a frequency band used by the relay station in order to receive thesignal from the relay UE may be identical with a frequency band used bythe relay station in order to transmit the signal to the BS (the sameprinciple applies to a case where the relay station is operated in a TDDmode or an FDD mode). A relay station cannot perform the transmissionand reception of signals at the same time in the same frequency bandbecause of self-interference. Accordingly, a relay station needs todistinguish a subframe used to receive a signal from a relay UE and asubframe used to transmit a signal to a BS. The guard time is placed foroperational stabilization switching when the transmission and receptionof signals are performed in the backhaul link and the access link. It isassumed that a relay station is unable to transmit or receive a signalin the guard time.

The guard time may be configured to the time of one symbol or less. Forexample, the guard time may be set to a ½ symbol, one symbol or thelike. If a relay station transmits a signal to a BS, the guard time hasto be taken into consideration in a backhaul UL subframe structure. Thatis, how resources will be allocated is problematic in the control regionor the data region of a backhaul UL subframe in which the number ofavailable symbols is reduced owing to the guard time. In other words,the structure of the backhaul UL subframe is problematic.

Furthermore, the allocation of resources to a reference signal (RS) isalso problematic within the backhaul UL subframe. The RS is used forchannel estimation. Channel estimation is necessary for user schedulingor data demodulation or both. Furthermore, the RS may be used to measurethe channel quality for its own cell or other cells, in addition tochannel estimation. The RS is known to both a transmitter and a receiverand is also called a pilot.

The RSs, in general, are transmitted in a sequence (this is called an RSsequence). Any sequence can be used as the RS sequence without specialrestrictions. A computer-generated sequence based on PSK (Phase ShiftKeying) may be used as the RS sequence. PSK can include, for example,BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying),and so on. Alternatively, a CAZAC (Constant Amplitude ZeroAuto-Correlation) sequence may be used as the RS sequence. The CAZACsequence can include, for example, a sequence based on ZC (Zadoff-Chu),a ZC sequence with cyclic extension, and a ZC sequence with truncation.Alternatively, a PN (Pseudo-random) sequence may be used as the RSsequence. The PN sequence can include, for example, m-sequence, acomputer-generated sequence, a Gold sequence, and a Kasami sequence.Furthermore, a cyclically shifted sequence may be used as the RSsequence.

The RS sequence R_(u,v) ^((α))(n) may be defined by Equation 1.

r _(u,v) ^((α))(n)=e ^(jan) r _(u,v)(n), 0≦n≦M _(SC) ^(RS)

In Equation 1, α is a cyclic shift, and r _(u,v)(n) is a basic sequence.M_(SC) ^(RS) is the length of the RS sequence. M_(SC) ^(RS)=m·N_(SC)^(RB), 1≦m≦N_(RB) ^(max,UL), and N_(SC) ^(RB) is the size of a resourceblock expressed by the number of subcarriers in the frequency domain.N_(RB) ^(max,UL) is a maximum uplink bandwidth configuration expressedby a multiple of N_(SC) ^(RB). A plurality of the RS sequences may bedefined by variously changing the cyclic shift a on the basis of asingle basic sequence.

The RS includes two kinds of signals, such as a DMRS (DemodulationReference Signal) and an SRS (Sounding Reference Signal). The DMRS is anRS used in channel estimation for demodulating a received signal. TheDMRS can also be called a dedicated RS, a user-specific RS, or the like.The DMRS may be associated with transmission of a PUSCH or a PUCCH. TheSRS is an RS transmitted from an MS to a BS for uplink scheduling. TheBS estimates an uplink channel through a received SRS and uses theestimated uplink channel for uplink scheduling. The SRS is notassociated with the transmission of a PUSCH or a PUCCH.

A sequence r^(PUSCH) of a DMRS for a PUSCH may be defined by Equation 2.

r ^(PUSCH)(m·M _(SC) ^(RS) +n)=r _(u,v) ^((α))(n)

In Equation 2, m=0, 1, n=0, . . . , M_(SC) ^(RS)−1, and M_(SC)^(RS)=M_(SC) ^(PUSCH)·M_(SC) ^(PUSCH) is a scheduled bandwidth foruplink transmission which is expressed by the number of subcarriers.R_(u,v) ^((α))(n) is an RS sequence. The r^(PUSCH) may be mapped to aresource block used for PUSCH transmission. The r^(PUSCH) may be mappedto a fourth (l=3) OFDM symbol from the front in case of the normal CPand to a third (l=2) OFDM symbol from the front in case of the extendedCP in each of the slots constituting a resource block. The DMRS may betransmitted through the mapped resources.

A sequence r^(SRS) of an SRS may be defined by Equation 3.

r ^(SRS)(n)=r _(u,v) ^((α))(n)

The sequence r^(SRS) is also mapped to a resource unit, and an SRS maybe transmitted through the resource unit. In 3GPP LTE uplink, a macro UEtransmits an SRS in the last symbol of a subframe. If a relay stationhas to transmit its own SRS, a relationship between guard time and anSRS transmitted by a macro UE has to be taken into consideration.

FIG. 7 is a diagram showing a timing relationship between subframes onwhich a base station receives a signal from a macro mobile station or arelay station.

FIG. 7( a) shows a subframe on which a BS receives a signal from a macroUE. This subframe is called a BS subframe.

FIG. 7( b) shows a backhaul UL subframe on which a relay stationtransmits a signal to a BS. The backhaul UL subframe has the same startposition and end position as those of a BS subframe in the time domain.That is, the backhaul UL subframe and the BS subframe have the sameboundary for every subframe in the time domain. Furthermore, the startposition and the end position of the backhaul UL subframe in the timedomain for every symbol are identical with the start position and theend position of the BS subframe in the time domain for every symbol. Inother words, the symbol boundary of the backhaul UL subframe isidentical with the symbol boundary of the BS subframe. The backhaul ULsubframe, having the same boundary as the BS subframe for every subframeand for every symbol as described above, is called a non-shiftingsubframe, for the sake of convenience. However, propagation delay,timing adjustment, and values that may vary according to a radio channelenvironment and a configuration between a BS and a relay station are notshown in the drawings. In the non-shifting subframe, 1) guard time maybe placed in the first symbol of a first slot and in the last symbol ofa second slot. Here, the number of available symbols that may be usedfor a relay station to transmit a control signal or data is 12 (in caseof a normal CP). In case of an extended CP, the number of availablesymbols is 10.

2) A guard time may be placed only in the first symbol of a first slot.Here, the number of available symbols that may be used for a relaystation to transmit a control signal or data is 13 (in case of a normalCP). In case of an extended CP, the number of available symbols is 11.

FIG. 7( c) shows a case where in which a backhaul UL subframe has thesame boundary as a BS subframe for every subframe, but does not have thesame boundary as the BS subframe for every symbol. That is, it may besaid that the boundary of the backhaul UL subframe for every symbol hasbeen backward shifted or forward by guard time as compared with theboundary of the BS subframe for every symbol. This subframe is called ashifting subframe. That is, the backhaul UL subframe shown in FIG. 7( c)is an example of the shifting subframe. FIG. 7( c) is for representingavailable symbols, and thus the start and end of the backhaul ULsubframe are not limited as in FIG. 7( c). However, the index of theforemost symbol of available symbols is not limited to 0 in terms of themanagement of the index of a symbol. Likewise, the index of the lastsymbol of available symbols is not limited to 13.

Like in the non-shifting subframe, even in the shifting subframe, theguard time may be allocated to the first and the last symbols of thebackhaul UL subframe or may be allocated to only the first symbol of thebackhaul UL subframe. For example, if the guard time is a ½ symbol, thenumber of symbols available for a relay station may be 13 in the formercase, and the number of symbols available for a relay station may be13.5 in the later case (in case of a normal CP).

The structures of the non-shifting subframe or the shifting subframe aredescribed below when a relay station transmits a signal to a BS in thenon-shifting subframe or the shifting subframe. For a clear description,radio resources allocated so that a macro UE can transmit a signal to aBS are also shown in the drawings. In the following drawings, a PUCCHand a PUSCH indicate a control channel and a data channel transmittedfrom a macro UE to a BS. An R-PUCCH (relay-PUCCH) indicates a controlchannel transmitted from a relay station to a BS, and an R-PUSCH(relay-PUSCH) indicates a data channel transmitted from a relay stationto a BS. Furthermore, in the following drawings, regions on the drawingswhere the PUCCH, the PUSCH, the R-PUCCH, and the R-PUSCH are displayedindicate that the relevant channels can be transmitted in relevant radioresource regions. A normal CP is described, for the sake of convenience,but it is evident that an extended CP may also be used.

Furthermore, in the following embodiments, an example in which each ofguard time placed in the first or the last or both of a subframe is a ½symbol is described, but not limited thereto.

FIG. 8 shows an example of the structure of a non-shifting subframe ifthe guard time is placed in the first symbol and the last symbol of thenon-shifting subframe.

R-PUCCHs and R-PUSCHs are allocated between the bands in which PUCCHsare transmitted in the frequency domain. Furthermore, the R-PUSCHs areallocated between the bands in which the R-PUCCHs are transmitted. Inthis case, the PUSCH may be allocated to a radio resource region towhich the R-PUSCH is not allocated. A relay station uses a shortenedR-PUCCH format because it has to transmit R-PUCCHs using 12 symbolsother than the guard time. The shortened R-PUCCH format means a formatthat transmits an RS and payloads using the number of symbols smallerthan the number of symbols of a PUCCH format.

For example, if an MS transmits an SRS in the last symbol of a subframe,the MS uses a shortened PUCCH format in which the last symbol ispunctured and only the remaining symbols are used. That is, in case of anormal CP, payloads, such as ACK/NACK, is not transmitted in the lastsymbol of 14 symbols. Like in the shortened PUCCH format, the R-PUCCHmay also use the shortened R-PUCCH format. The shortened R-PUCCH formatwill be described in detail later.

An RB (Resource Block) to which an R-PUCCH is allocated is differentfrom an RB to which a PUCCH is allocated. A link between a BS and arelay station and a link between a BS and an MS have different channelconditions. Accordingly, if the R-PUCCH and the PUCCH are allocated tothe same RB, the orthogonality of an orthogonal sequence may be broken.Furthermore, it may be difficult to multiplex the R-PUCCH and the PUCCHto the same RB because the R-PUCCH and the PUCCH have differentstructures according to how the backhaul subframe structure is defined.It is therefore preferred that the R-PUCCH and the PUCCH use differentRBs.

FIG. 9 shows another example of the structure of a non-shifting subframeif the guard time is placed only in the first symbol of the non-shiftingsubframe.

A relay station may transmit R-PUCCHs using a shortened R-PUCCH formatbecause the number of available symbols within a subframe is 13. Here,unlike in the shortened PUCCH format, symbols remained after a firstsymbol is punctured instead of a last symbol are allocated to a firstslot, and there is no change in a second slot. The indices of thesymbols included in the first slot may be backward shifted by one symbollike 0 to 5 instead of 1 to 6.

A guard time may be placed in a subsequent subframe because there is noguard time in the last symbol of the subframe. Accordingly, a relaystation may not receive some access signals in the subsequent subframe.

FIG. 10 shows an example of the structure of a shifting subframe if theguard time is placed in the first symbol and the last symbol of theshifting subframe.

A relay station transmits R-PUCCHs and R-PUSCHs to a BS right after alapse of the first guard time 101 of the subframe, unlike in thenon-shifting subframe. Accordingly, the amount of wasted radio resourcescan be reduced. If each guard time is smaller than one symbol (e.g., a ½symbol), interference may be generated because the boundary of symbolson which a macro UE sends a signal is not identical with the boundary ofsymbols on which a relay station sends a signal. Accordingly, the relaystation may use a shortened R-PUCCH format because the number ofavailable symbols is reduced owing to the guard time. The number ofsymbols available for the relay station is 13.

FIG. 11 shows another example of the structure of a shifting subframe ifthe guard time is placed only in the first symbol of a subframe.

Unlike in FIG. 10, a relay station may use 13 or more symbols in case ofa normal CP. For example, if the guard time is a ½ symbol, a relaystation may use 13.5 symbols. A relay station may transmit a controlsignal using a shortened R-PUCCH format in 13 symbols. ½ symbols 111 and112 placed in the last of the subframes in the frequency bands in whichrespective R-PUSCHs are transmitted may be used to transmit R-PUSCHs ormay be used for other special purposes.

In the backhaul UL subframes described with reference to FIGS. 8 to 11,radio resources to which the R-PUCCHs are allocated may be related tothe R-PDCCHs. For example, a CCE index to which an R-PUCCH is allocatedmay be determined according to a CCE index on which an R-PDCCH istransmitted. Furthermore, unlike in the existing 3GPP LTE, both theR-PUCCH and the R-PUSCH may be transmitted at the same time. An RB onwhich the R-PUCCH is transmitted is different from an RB on which aPUCCH is transmitted. That is, the R-PUCCH and the PUCCH are transmittedthrough different radio resources.

Furthermore, a relay station may signalize BSI (Buffer StatusInformation) through an R-PUCCH. If an R-PUCCH is not transmitted, theBSI may be signalized through a higher layer signal or may bepiggybacked in R-PUSCH transmission.

Furthermore, as described above, in the backhaul UL subframe structure,the number of symbols available for a relay station is reduced owing tothe guard time. The R-PUCCH requires a new structure because the numberof symbols available for the R-PUCCH is different from the number ofsymbols available for PUCCHs. That is, it is necessary to newly definethe positions and the number of symbols to which an RS and payloads,such as ACK/NACK, SR, and CQI transmitted through the R-PUCCHs, areallocated. The newly defined R-PUCCH format is called a shortenedR-PUCCH format. The shortened R-PUCCH format is described below by wayof a detailed example in which the RS and the payloads transmittedthrough the R-PUCCHs are allocated.

FIG. 12 shows examples of shortened R-PUCCH formats in the non-shiftingsubframe.

The guard time is placed in the first symbol and the last symbol of thesubframe. A relay station may transmit an RS and payloads in the symbolperiod other than the first symbol of a first slot and in the lastsymbol of a second slot.

Referring to FIG. 12, in a shortened R-PUCCH format 1/1a/1b, in a normalCP, a DMRS may be transmitted in the symbols #2, 3, and 4 of each slot,and a payload may be transmitted in the symbols #1, 5, and 6 of a firstslot and the symbols #0, 1, and 5 of a second slot. In an extended CP,the DMRS may be transmitted in the symbols #2 and 3 of each slot, andthe payload may be transmitted in the symbols #1, 4, and 5 of a firstslot and in the symbols #0, 1, and 4 of a second slot. In FIG. 12, ifthe guard time is placed in the last symbol of the second slot, theexisting shortened PUCCH format 1/1a/1b may be reused in the secondslot. For comparison purposes, however, the shortened format isillustrated to be used both in the first slot and the second slot.

In case of a shortened R-PUCCH format 2/2a/2b, in a normal CP, a DMRSmay be transmitted in the symbols #1 and 5 of each slot, and a payloadmay be transmitted in the symbols #2, 3, 4, and 6 of a first slot and inthe symbols #0, 2, 3, and 4 of a second slot. In an extended CP, theDMRS may be transmitted in the symbol #3 of each slot, and the payloadmay be transmitted in the symbols #1, 2, 4, and 5 of a first slot and inthe symbols #0, 1, 2, and 4 of a second slot. If the guard time isplaced in the last symbol of the second slot, the existing availablePUCCH format 2/2a/2b has not been defined. The shortened R-PUCCH format2/2a/2b may be applied to only one of the two slots within the subframe.For example, the shortened R-PUCCH format 2/2a/2b may be applied to onlythe first slot of the subframe or may be applied to both the two slotsof the subframe. That is, in the shortened R-PUCCH formats proposed inFIG. 12, a form in which available symbols are reduced in both the firstslot and the second slot may be used, or a form in which availablesymbols are reduced only in the first slot for the degree of freedom ofan operation may be used. The two methods may be implemented so thatthey are configured by higher layer signaling.

That is, the shortened R-PUCCH format of FIG. 12 is the same as thePUCCH format used by an MS except the symbol where the guard time isplaced. In other words, the shortened R-PUCCH format is the same as thePUCCH format in the position where the RS is placed, but in theshortened R-PUCCH format, the payload may be allocated to a symbolperiod other than the first symbol and the last symbol of a subframewhich cannot be used owing to the guard time.

FIG. 13 shows another example of shortened R-PUCCH formats in thenon-shifting subframe.

A guard time is placed only in the first symbol of the subframe. Theguard time is illustrated to be a ½ symbol, but may be one symbol. Inthe shortened R-PUCCH format, an RS and a payload may be allocated tosymbols other than the first symbol of a first slot. FIG. 13 isdifferent from FIG. 12 in that the RS or the payload may be transmittedin the last symbol of the subframe. The shortened R-PUCCH format isadvantageous in that an SRS can be transmitted in the last symbol of asecond slot. Alternatively, in the shortened R-PUCCH format, a shortenedPUCCH format used in 3GPP LTE may be shifted by one symbol and thenallocated to available symbols. This is possible by designating theindices of available symbols as 0 to 12, if symbol indices within asubframe are sequentially designated as 0 to 13 (in a normal CP).

FIG. 14 shows examples of shortened R-PUCCH formats in a shiftingsubframe.

The shortened R-PUCCH format may include different numbers of symbols ina first slot and a second slot. 7 symbols may be included in the firstslot and 6 symbols may be included in the second slot as shown in FIG.14( a), and 6 symbols may be included in the first slot and 7 symbolsmay be included in the second slot as shown in FIG. 14( b) (in case of anormal CP).

The shortened R-PUCCH format may be a format in which a shortened PUCCHformat used in an MS is backward shifted by a ½ symbol and a payloadallocated to the last symbol of a slot, from among payloads, is thenpunctured. The shortened R-PUCCH format may be a format in which, asshown in FIG. 14( a), the last symbol of the second slot to which thepayload is allocated is punctured and the RSs or the payloads areallocated to only the 6 symbols of the second slot (in case of theshortened R-PUCCH format 1/1a/1b). Alternatively, the shortened R-PUCCHformat may be a format in which, as shown in FIG. 14( b), the lastsymbol of the first slot to which the payload is allocated is puncturedand the RSs or the payloads are allocated to only the 6 symbols of thefirst slot (in case of the shortened R-PUCCH format 1/1a/1b).

FIG. 15 shows another example of shortened R-PUCCH formats in a shiftingsubframe.

FIG. 15( a) is different from FIG. 14( a) in that the position of an RSallocated to a second slot has been forward shifted by one symbol. FIG.15( b) is different from FIG. 14( b) in that the position of an RSallocated to a first slot is forward shifted by one symbol.

FIG. 16 shows yet another example of shortened R-PUCCH formats in ashifting subframe.

In a shortened R-PUCCH format 1/1a/1b, any one of RS symbols placed in afirst slot or a second slot is punctured. For example, an RS symbolplaced in the symbol #4 of the second slot may be punctured and RSs maybe placed only in the symbols #2 and #3 of the second slot in a normalCP as in FIG. 16( a), or an RS symbol placed in the symbol #4 of thefirst slot may be punctured and RSs may be placed only in the symbols #2and #3 of the first slot as in a normal CP as in FIG. 16( b). FIG. 16 isdifferent from FIGS. 14 and 15 in that not the payload, but the RS ispunctured.

FIG. 17 shows examples of shortened R-PUCCH formats if the guard time isplaced only in the first slot of a subframe in a shifting subframe.

The number of symbols available for a relay station is 13 or morebecause the guard time is placed in the first slot of the subframe. Forexample, if the guard time is a ½ symbol, a relay station may use 13.5symbols. A relay station may puncture the last payload of a first slotor a second slot. FIG. 17( a) shows an example in which the last payloadof the first slot is punctured (i.e., a payload allocated to the symbol#6 of the first slot is punctured), and FIG. 17( b) shows an example inwhich the last payload of the second slot is punctured (i.e., a payloadallocated to the symbol #6 of the second slot is punctured).

FIG. 17 shows an example in which the guard time is a ½ symbol. However,the guard time may be one symbol. In this case, a ½ symbol placed in thelast slot of the subframe may do not exist.

FIG. 18 shows another example of shortened R-PUCCH formats if the guardtime is placed only in the first slot of a subframe in a shiftingsubframe.

FIG. 18 is different from FIG. 17 in that one payload is punctured inthe first slot or the second slot, but the first payload of each slot ispunctured. Consequently, FIG. 18( a) is different from FIG. 17( a) inthat the position of an RS in the first slot is forward shifted andallocated by one symbol. FIG. 18( b) is different from FIG. 17( b) inthat the position of an RS in the second slot is forward shifted andallocated by one symbol.

FIG. 19 shows yet another example of shortened R-PUCCH formats if theguard time is placed only in the first slot of a subframe in a shiftingsubframe.

FIG. 19 is different from FIG. 17 in that one RS symbol is punctured inthe first slot or the second slot. That is, in FIG. 19( a), in a normalCP, one of RS symbols allocated to the first slot is punctured. In FIG.19( b), in a normal CP, one of RS symbols allocated to the second slotis punctured. The number of symbols to which payloads are allocated inthe first slot is identical with the number of symbols to which payloadsare allocated in the second slot, and the number of symbols to which RSsallocated in the first slot is different from the number of symbols towhich RSs allocated in the second slot.

Meanwhile, if the first symbol of a subframe is punctured, the startposition of a second symbol in a normal CP is different from the startposition of a second symbol in an extended CP. In this case, in order toforcedly make identical the boundaries of the two symbols with eachother, additional timing offset signaling may be applied. Alternatively,the boundary of the symbol may be obtained through a blind searchingprocess according to the type of each CP despite some complexityincrease.

Even in case of an R-PUSCH through which a relay station transmitsuplink data to a BS, the fact that the number of symbols available in abackhaul link is reduced owing to the guard time must be taken intoaccount. Accordingly, the R-PUSCH may use a shortened R-PUSCH formatwhich is a format having the smaller number of symbols than a PUSCHformat through which an MS transmits data to a BS. A RS structure usedin the shortened R-PUSCH format may be identical with an RS structureused in the PUSCH format in which an MS transmits data to a BS, exceptsymbols used in the guard time. This is called a deletion type RSstructure.

Alternatively, the RS structure used in the shortened R-PUSCH format mayuse a method of shifting the deletion type RS structure. This may bedetermined according to whether a backhaul UL subframe is a shiftingsubframe or a non-shifting subframe. If one symbol has been deleted, theindices of R-PUSCH symbols may be assigned 0 to 12 or 1 to 13.Accordingly, the indices of RSs may also be changed.

The RS structure used in the shortened R-PUSCH format may be one symboltype in which an RS is transmitted only in the one symbol of each slotor a type determined according to a resource element (RE) pattern. Thatis, this is a method of transmitting RSs allocated to some REs, REgroups, and resources blocks (RBs) including REs in a pattern form, notconsecutively. The RSs are transmitted only in relevant relay station orrelevant resources.

A method of allocating radio resources in order to transmit an R-SRS ina backhaul UL subframe is described below.

FIG. 20 shows an example in which radio resources are allocated in orderto transmit an R-SRS in a non-shifting subframe. The example shows thatthe guard time is placed in the first symbol and the last symbol of thesubframe. FIG. 20 shows an example in which propagation delay, timingoffset, and adjustment values are not shown. If propagation delay,timing offset, and adjustment values are taken into consideration, thestart and end of available symbols of backhaul channels may be differentfrom those shown in FIG. 20. For example, if the sum total ofpropagation delay and timing adjustment values is a ½ symbol, the startof available symbols may be behind a ½ symbol.

Assuming that the entire frequency band through which a relay stationtransmits R-PUCCHs or R-PUSCHs to a BS is a relay zone (this ishereinafter the same), PUSCHs on which a macro UE transmits data to theBS within the relay zone may be determined not to be included.

In this case, the relay station may transmit the R-SRS to the BS throughsymbols different from those of an SRS transmitted by the macro UE inthe time domain. For example, the relay station may transmit the R-SRSin the second symbol from the last of a second slot (i.e., the symbol #5of the second slot). The relay station may transmit the R-SRS to the BSover the entire relay zone in the frequency domain. Here, the SRS may betransmitted in the bands in which PUCCHs and PUSCHs are transmitted.Accordingly, the BS has only to receive the SRS in the last symbol of asubframe and to perform channel estimation in relation to the macro UEas in the prior art and has only to receive the R-SRS in the secondsymbol from the last of the subframe and to perform channel estimationin relation to the relay station.

FIG. 21 shows another example in which radio resources are allocated inorder to transmit an R-SRS in a non-shifting subframe.

Unlike FIG. 20, FIG. 21 may include PUSCHs transmitted by a macro UEwithin the relay zone. For example, the PUSCHs may be allocated betweenbands in which R-PUCCHs are transmitted. In this case, a relay stationmay transmit the R-SRS to a BS only in relation to the bands in whichthe R-PUSCHs are transmitted in the frequency domain. The SRS may betransmitted in the bands in which the PUCCH, the R-PUCCH, and the PUSCHare transmitted.

A relay station may transmit the R-SRS to a BS through symbols differentfrom those of an SRS transmitted by a macro UE in the time domain. Forexample, a relay station may transmit the R-SRS in a second symbol fromthe last of a second slot (the symbol #5 of the second slot in a normalCP, and the symbol #4 of the second slot in an extended CP). In thiscase, interference can be minimized by avoiding overlapping with theexisting SRS, and multiplexing performance between the existing SRSusers is not degraded.

FIG. 22 shows yet another example in which radio resources are allocatedin order to transmit an R-SRS in a non-shifting subframe.

Unlike in FIG. 21, in FIG. 22, the R-SRS is transmitted over the entirerelay zone. That is, the R-SRS is transmitted even in the band to whichPUSCHs included in the relay zone are allocated. A relay station maytransmit the R-SRS to a BS through symbols different from those of anSRS transmitted by a macro UE in the time domain. For example, a relaystation may transmit the R-SRS in a second symbol from the last of asecond slot.

It is preferred that the band to which the PUSCHs included in the relayzone are allocated be for only an LTE-A UE. That is, allocation to theLTE MS may be prohibited. If the R-SRS is transmitted within the relayzone as described above, the MS should not transmit uplink data in asecond symbol from the last of a subframe. If both the R-SRS and the SRSare transmitted, the MS should not transmit uplink data in the lastsymbol of the subframe and in the second symbol from the last of thesubframe. In order to transmit uplink data using symbols reduced asdescribed above, new rate matching, coding, and interleaving may beused. Accordingly, it is preferred that the uplink data be transmittedin the band to which the PUSCHs included in the relay zone are allocatedin relation to only the LTE-A MS. The same rule may be applied to theSRS or the PUSCHs that must be multiplexed with the R-SRS in a relevantsubframe period irrespective of whether the R-SRS is transmitted in whatfrequency band.

In view of characteristic of a backhaul link using resources in TDM, afirst symbol, a last symbol, or other symbols may not be actually usedfor transmission. The symbols are not used as the resources of thebackhaul link, but an MS designed to use the symbols may use the symbolsfor uplink transmission. For example, if a relay station does not usethe first symbol of a subframe, the first symbol of the subframe may beallocated to the uplink transmission of a macro UE because the firstsymbol of a resource block (RB) used by the relay station is all wasted.

FIG. 23 shows examples of shortened R-PUCCH formats if an SRS and anR-SRS are transmitted in a non-shifting subframe.

The shortened R-PUCCH format is the same as the PUCCH format in a schemefor allocating RSs and payloads in each slot, but may be configured tohave a format in which a symbol including guard time and a symbol towhich an R-SRS or an SRS is allocated are punctured.

For example, in case of a normal CP, a shortened R-PUCCH format type Adoes not use the first symbol of a first slot owing to the guard time. ADMRS may be allocated to the symbols #2, 3, and 4 of each slot, and apayload may be allocated to the symbols #1, 5, and 6 of a first slot andthe symbols #0 and 1 of a second slot. In case of an extended CP, theDMRS may be allocated to the symbols #2 and 3 of each slot, and thepayload may be allocated to the symbols #1, 4, and 5 of a first slot andthe symbols #0 and 1 of a second slot. In case of the normal CP, anR-SRS is allocated to the symbol #5 of the second slot and an SRS isallocated to the symbol #6 of the second slot. In case of the extendedCP, the R-SRS is allocated to the symbol #4 of the second slot, and theSRS is allocated to the symbol #5 of the second slot. That is, theshortened R-PUCCH format type A is the same as the PUCCH format 1/1a/1bin a scheme for allocating the RSs and the payloads, but may beconfigured to have a format in which a symbol including the guard timeand a symbol to which the R-SRS or the SRS is allocated are punctured.

In a shortened R-PUCCH format type B, in a normal CP, a DMRS isallocated to the symbols #1 and 5 of a first slot and only the symbol #1of a second slot. In an extended CP, the DMRS may be allocated to thesymbol #3 of the first slot and the symbol #3 of the second slot. Thatis, the shortened R-PUCCH format type B is the same as the PUCCH format2/2a/2b in a scheme for allocating the RSs and the payloads, but may beconfigured to have a format in which a symbol including the guard timeand a symbol to which the R-SRS or the SRS is allocated are punctured

FIG. 24 shows another example of shortened R-PUCCH formats if an SRS andan R-SRS are transmitted in a non-shifting subframe.

In the shortened R-PUCCH format, a scheme for allocating RSs andpayloads may be different for every slot.

For example, in a shortened R-PUCCH format type A, in case of a normalCP, the first symbol of a first slot is not used owing to the guardtime. A DMRS is allocated to the symbols #2, 3, and 4 of the first slotand the symbols #2 and 3 of a second slot. A payload may be allocated tothe symbols #1, 5, and 6 of the first slot and the symbols #0, 1, and 4of the second slot. In case of an extended CP, the DMRS may be allocatedto the symbols #2 and 3 of a first slot and the symbol #2 of a secondslot. The payload may be allocated to the symbols #1,4, and 5 of thefirst slot and the symbols #0, 1, and 3 of the second slot. In case of anormal CA, an R-SRS is allocated to the symbol #5 of the second slot,and an SRS is allocated to the symbol #6 of the second slot. In case ofan extended CP, the R-SRS is allocated to the symbol #4 of the secondslot, and the SRS is allocated to the symbol #5 of the second slot.

In a shortened R-PUCCH format type B, in case of a normal CP, a DMRS maybe allocated to the symbols #1 and 5 of a first slot and the symbols #1and 3 of a second slot. In case of an extended CP, a DMRS may beallocated to the symbol #3 of the first slot and the symbol #2 of thesecond slot. A payload may be allocated to symbols other than thesymbols to which the DMRS, the first symbol of the first slot, theR-SRS, and the SRS are allocated.

FIG. 25 shows examples of shortened R-PUCCH formats having symmetricstructures on the basis of a slot boundary if only an SRS is transmittedin a non-shifting subframe.

Referring to FIG. 25, the shortened R-PUCCH format may be a format inwhich an RS and a payload are symmetrically allocated on the basis of aslot boundary. For example, in a shortened R-PUCCH format type A, incase of a normal CP, a DMRS may be allocated to a symbol spaced from theslot boundary by two symbols or three symbols. That is, the DMRS may beallocated to the symbols #3 and 4 of a first slot and the symbols #2 and3 of a second slot. The payload may be allocated to the remainingsymbols other than symbols to which the guard time are allocated andsymbols to which the DMRSs are allocated, in the subframe.

A relay station cannot use the first symbol and the last symbol of asubframe in order to transmit a signal because the guard time is placedin the first symbol and the last symbol of the subframe. If an SRS istransmitted in the last symbol of the subframe and a relay station doesnot transmit an R-SRS, the relay station may symmetrically allocate theRS and the payload on the basis of the slot boundary. In this case, therelay station may use the shortened R-PUCCH format described withreference to FIG. 25.

FIG. 26 shows examples of shortened R-PUCCH formats having symmetricstructures on the basis of a slot boundary, if an SRS and an R-SRS aretransmitted in a non-shifting subframe.

In a shortened R-PUCCH format type A, in case of a normal CP, a DMRS maybe allocated to the symbols #3 and #4 of a first slot and the symbols #2and #3 of a second slot. A payload may be allocated to the symbols #1,#2, #5, and #6 of the first slot and the symbols #0, #1, and #4 of thesecond slot.

The DMRS or the payload cannot be allocated to the last 2 symbols of thesecond slot because an R-SRS and an SRS are sequentially placed in thelast 2 symbols of the second slot. The DMRS or the payload cannot beallocated to the first symbol of the first slot because the guard timeis placed in the first symbol of the first slot. Under the aboverestriction, a relay station may symmetrically allocate the DMRS and thepayload according to a shortened R-PUCCH format having the abovesymmetric structure. FIG. 26 is different from FIG. 25 in that thesecond symbol from the last of the second slot is not used.

In the shortened R-PUCCH formats having the symmetric structuredescribed with reference to FIGS. 25 and 26, a case where symbols placedat both ends of a backhaul UL subframe cannot be used has been takeninto consideration. Orthogonal sequences used in the shortened R-PUCCHformat having the above symmetric structure may also be symmetrical toeach other on the basis of the slot boundary. The orthogonal sequencesmay be used for spreading for increasing the multiplexing capacity.

FIG. 27 shows an example in which the orthogonal sequence is applied tothe shortened R-PUCCH format having the symmetric structure.

In the shortened R-PUCCH format, for example, payloads, such asACK/NACK, may be allocated to the symbols #1, 2, 5, and 6 of a firstslot and the symbols #0, 1, 4, and 5 of a second slot, and an RS may beallocated to the symbols #3 and 4 of the first slot and the symbols #2and 3 of the second slot. In this case, in order to transmit theACK/NACK signal, the ACK/NACK signal of 2 bits is subjected to QPSKmodulation to produce one modulation symbol d(0). A modulated sequencem(n) may be generated as in Equation 4 on the basis of the modulationsymbol d(0) and a cyclically shifted sequence r(n,a).

m(n)=d(0)·r(n,a)

In Equation 4, the cyclically shifted sequence r(n,a) refers to asequence obtained by cyclically shifting a sequence r(n) by a. Themodulated sequence m(n) may be generated by multiplexing the cyclicallyshifted sequence r(n,a) by a modulation symbol. The modulated sequencem(n) may be spread using an orthogonal sequence. The following sequencemay be used as an orthogonal sequence w_(i)(k) (i is a sequence index,0≦k≦K−1) having a spreading factor of K=4.

SEQUENCE INDEX [W(0), W(1), W(2), W(3)] 0 [+1 +1 +1 +1] 1 [+1 −1 +1 −1]2 [+1 −1 −1 +1]

In this case, in the orthogonal sequence, the same value is applied to asymmetrical symbol on the basis of a slot boundary. For example,w_(i)(3) may be applied to the symbol #6 of a first slot and the symbol#0 of a second slot, w_(i)(2) may be applied to the symbol #5 of thefirst slot and the symbol #1 of the second slot, w_(i)(1) may be appliedto the symbol #2 of the first slot and the symbol #4 of the second slot,and w_(i)(0) may be applied to the symbol #1 of the first slot and thesymbol #5 of the second slot.

The conventional method is a method of sequentially applying orthogonalsequence values in each slot. In the conventional method, if theorthogonal sequence value cannot be applied to the first symbol of thefirst slot and the last symbol of the second slot, complexity may beincreased because a different orthogonal sequence value is applied toeach slot. However, if the orthogonal sequence values are symmetricallyapplied on the basis of the slot boundary, the probability that theorthogonal sequence values applicable to the first slot and the secondslot may be the same is high. Accordingly, complexity is reduced.

An example in which the orthogonal sequence has the spreading factor K=4has been described with reference to FIG. 27, but not limited thereto.For example, the following sequence may be used as an orthogonalsequence w_(i)(k) (i is a sequence index, 0≦k≦K−1) having a spreadingfactor K=3.

SEQUENCE INDEX [W(0), W(1), W(2)] 0 [1 1 1] 1 [1 e^(j2π/3) e^(j4π/3)] 2[1 e^(j4π/3) e^(j2π/3)]

Alternatively, the following sequence may be used as an orthogonalsequence w_(i)(k) (i is a sequence index, 0≦k≦K−1) having a spreadingfactor K=2.

SEQUENCE INDEX [w(0), w(1)] 0 [1 1] 1 [1 −1]

Alternatively, the following sequence may be used as an orthogonalsequence w_(i)(k) (i is a sequence index, 0≦k≦K−1) having a spreadingfactor K=1.

SEQUENCE INDEX [w(0)] 0 [1]

FIG. 28 shows an example of a subframe structure if an R-SRS istransmitted in a shifting subframe.

PUSCHs transmitted from a macro UE to a BS within a relay zone may bedetermined not to be included. In this case, a relay station maytransmit the R-SRS to the BS through symbols deviated from SRSs,transmitted by the macro UE, by the guard time in the time domain. Therelay station may transmit the R-SRS to the BS over the entire relayzone in the frequency domain. The SRSs may be transmitted in the bandsin which PUCCHs and the PUSCHs are transmitted. FIG. 28 is differentfrom FIG. 20 in that a symbol is deviated by guard time in the relayzone.

FIG. 29 shows another example of a subframe structure if an R-SRS istransmitted in a shifting subframe.

FIG. 29 may include PUSCHs transmitted by a macro UE within a relayzone, unlike FIG. 28. For example, the PUSCHs may be allocated betweenthe bands in which R-PUCCHs are transmitted and the bands in whichR-PUSCHs are transmitted. In this case, a relay station may transmit theR-SRS to a BS only in the bands in which the R-PUSCHs are transmitted inthe frequency domain.

The relay station may transmit the R-SRS to the BS through symbolsdeviated from the SRSs, transmitted by the macro UE, by the guard timein the time domain. FIG. 29 is different from FIG. 21 in that a symbolboundary is shifted by the guard time in the R-PUCCHs and the R-PUSCHsincluded in the relay zone.

FIG. 30 shows an example of a subframe structure if the guard time isplaced only in the first symbol and an R-SRS is transmitted in anon-shifting subframe.

If the guard time is placed only in the first symbol in the non-shiftingsubframe, the R-SRS may be transmitted in the last symbol of a secondslot. That is, a relay station may transmit the R-SRS in the last symbolof the subframe in the time domain. In other words, the relay stationmay transmit the R-SRS in the same symbol as a symbol through which anMS transmits an SRS to a BS. The relay station may transmit the R-SRSonly in the bands in which R-PUSCHs are transmitted in the relay zone.The SRS may be transmitted in the bands in which PUCCHs, the R-PUCCHs,and PUSCHs are transmitted.

FIG. 31 shows another example of a subframe structure if the guard timeis placed only in the first symbol and an R-SRS is transmitted in anon-shifting subframe.

Like in FIG. 30, if the guard time is placed only in the first symbol inthe non-shifting subframe, the R-SRS may be transmitted in the lastsymbol of a second slot. That is, a relay station may transmit the R-SRSthe last symbol of the subframe in the time domain. FIG. 31 is differentfrom FIG. 30 in that a PUSCH band is not included in the relay zone andthe R-SRS is transmitted over the entire relay zone.

FIG. 32 shows yet another example of a subframe structure if the guardtime is placed only in the first symbol and an R-SRS is transmitted in anon-shifting subframe.

Like in the embodiment described with reference to FIG. 31, if the guardtime is placed only in the first symbol in the non-shifting subframe,the R-SRS may be transmitted in the last symbol of a second slot. Thatis, a relay station may transmit the R-SRS in the last symbol of thesubframe in the time domain. FIG. 32 is different from FIG. 31 in thatthe R-SRS is transmitted only in the bands in which R-PUSCHs aretransmitted in the relay zone. Furthermore, FIG. 32 is different fromFIG. 31 in that both the R-SRS and the SRS are not transmitted in theband in which R-PUCCHs are transmitted. That is, the last symbol of thesecond slot may be use to transmit a payload or a DMRS in the band inwhich the R-PUCCH is transmitted.

FIGS. 33 and 34 show still another example of subframe structures if theguard time is placed only in the first symbol and an R-SRS istransmitted in a non-shifting subframe.

A difference between FIG. 33 and FIG. 34 lies in that whether a PUSCHband can be included in the relay zone. That is, whether regions notallocated to transmit R-PUCCHs and R-PUSCHs can be reused to transmitthe PUSCH in the relay zone. FIG. 33 shows a case where bands notallocated for R-PUCCH transmission and R-PUSCH transmission in the relayzone are reused for PUSCH transmission, and FIG. 34 shows a case wherethe bands not allocated for the R-PUCCH transmission and the R-PUSCHtransmission in the relay zone are not reused for the PUSCHtransmission.

The R-SRS may be transmitted in the last symbol of a second slot becausethe guard time is placed only in the first symbol of the non-shiftingsubframe. That is, a relay station may transmit the R-SRS in the lastsymbol of the subframe in the time domain. In this case, the R-SRS andan SRS are multiplexed over the entire system in the last symbol of thesubframe. A method of multiplexing the R-SRS and the SRS is describedbelow.

FIG. 35 shows a method of multiplexing the R-SRS and the SRS in thesubframe structures of FIGS. 33 and 34.

In the entire system band, subcarriers or resource elements can besequentially indexed. In this case, a subcarrier having an even indexmay be allocated to transmit the SRS, and subcarrier having an odd indexmay be allocated to transmit the R-SRS. The opposite is also possible.

Alternatively, a subcarrier having an index of a multiple of an integernumber may be allocated to transmit the R-SRS. For example, a subcarrierhaving an index of 4*N (N is a natural number) may also be allocated totransmit the R-SRS.

Alternatively, the subcarriers may also be allocated so that a pluralityof the R-SRSs is distinguished from each other. For example, if fourrelay stations transmit respective R-SRSs in the same symbol, asubcarrier having an index (8m+1) may be allocated to the relay station1, a subcarrier having an index (8m+3) may be allocated to the relaystation 2, a subcarrier having an index (8 m+5) may be allocated to therelay station 3, and a subcarrier having an index (8 m+7) may beallocated to the relay station 4 in the entire system band so that therelay stations may use the respective subcarriers to transmit the R-SRSs(where m=0, 1, 2, . . . ). Here, a subcarrier having an even index maybe allocated to transmit an SRS. Here, the relay stations 1, 2, 3, and 4may be different relay stations or the same relay station. If the relaystations 1, 2, 3, and 4 are the same relay station, it may mean that aplurality of R-SRSs is transmitted from one relay station.

In the above example, in order to avoid a collision between the SRS andthe R-SRS, the subcarrier allocated to the R-SRS may not be allocated tothe SRS. To this end, a parameter for distinguishing the subcarriers onwhich the SRS and the R-SRS are transmitted from each other may betransmitted through a higher layer signal, such as RRC signaling. Forexample, if a value of the parameter is 0, it may indicate thesubcarrier on which the SRS is transmitted. If a value of the parameteris 1, it may indicate the subcarrier on which the R-SRS is transmitted.

A method of allocating the SRS and the R-SRS to different subcarriers inthe entire system band, allocating the R-SRS to subcarriers placedbetween subcarriers to which the SRS is allocated, and then multiplexingthe SRS and the R-SRS as described above is called a transmission comb,for the sake of convenience.

In each of the subframe structures described with reference to FIGS. 28to 34, the relay zone or the band in which the R-PUSCH is transmittedmay be configured semi-statically.

A case where the placement of guard time between two consecutivesubframes is unnecessary is described, and a method of utilizing radioresources generated because the guard time is not placed is described.

The following table shows a case where the guard time is necessary and acase where the guard time is unnecessary.

Subframe Need for guard Config- time between two uration 1^(st) subframe2^(nd) subframe subframes FDD/TDD Access UL (Rx) Backhaul UL (Tx) Yes ULto UL Backhaul UL (Tx) Access UL (Rx) Yes Backhaul UL (Tx) Backhaul UL(Tx) No TDD Backhaul DL (Rx) Backhaul UL (Tx) Yes DL to UL Access DL(Tx) Backhaul UL (Tx) Yes TDD Backhaul UL (Tx) Backhaul DL (Rx) Yes ULto DL Backhaul UL (Tx) Access DL (Tx) Yes

Referring to the above table, the placement of guard time between twoconsecutive subframes is unnecessary only when a relay station transmitsa signal to a BS in the first subframe and then transmits a signal tothe BS even in the second subframe in FDD or TDD.

FIG. 36 shows radio resources generated when the placement of the guardtime between two consecutive subframes is unnecessary in relation to anon-shifting subframe and a shifting subframe. FIG. 36( a) shows thenon-shifting subframe, and FIG. 36( b) shows the shifting subframe.

Radio resources generated between two consecutive subframes becauseguard time is not placed are called special resources. The specialresources may be used for various purposes. For example, the specialresources may be used for an R-PUSCH, an R-PUCCH, BSI reporting, and anSRS. If the special resources are used for an R-PUSCH, an R-PUCCH, BSIreporting, and an SRS, relevant information may be transmittedaperiodically or in a fixed cycle.

Aperiodic BSI reporting may be scheduled like in 3GPP LTE release 8.

FIG. 37 shows a subframe structure in which an R-PUCCH and R-PUSCHs aresubjected to TDM if the guard time is placed in the first symbol and thelast symbol of a non-shifting subframe.

A relay zone is allocated to a specific frequency band between frequencybands in which PUCCHs are transmitted. That is, the relay zone may beallocated to a frequency band in which a PUSCH is transmitted.

The R-PUCCH and the R-PUSCH are subjected to TDM within the relay zone.That is, the R-PUCCH and the R-PUSCH are distinguished from each otherin the time domain. A relay station may not use a first symbol or a lastsymbol or both within the relay zone to transmit a signal because guardtime is placed in the first symbol or the last symbol or both.Furthermore, frequency bands may be distinguished from each other forevery relay station within the relay zone and then allocated.

The R-PUCCH is not necessarily transmitted within a frequency bandallocated to each relay station. For example, in FIG. 37, in case of arelay station 1 RS #1, the R-PUCCH is not transmitted, but only theR-PUSCH is transmitted in the allocated frequency band. In case of arelay station 2 RS #2, both the R-PUCCH and the R-PUSCH are transmittedin the allocated frequency band. If the R-PUCCH is not transmitted,relevant radio resources 371 may be used to transmit the R-PUSCH. Theradio resources 371 may be a resource element or a CDM (code divisionmultiplexing) resource element. The CDM resource element may be usedwhen a plurality of payloads (e.g., a plurality of ACK/NACK) has to betransmitted in the radio resources 371.

Alternatively, the relevant radio resources 371 may be left for R-PUCCHtransmission although the R-PUCCH is not actually transmitted. A CCEindex to which the R-PUCCH is allocated may be determined by the CCEindex of the R-PDCCH. The radio resources 371 are hereinafter called areservation region.

The R-PUSCH may use only a smaller number of symbols than that of aPUSCH owing to guard time and symbols on which the R-PUCCH istransmitted in the time domain. The number of symbols used in theR-PUSCH may be set to a specific number in order to reduceimplementation complexity or a different number of symbols may be usedfor every relay station.

FIG. 37 illustrates the case where the guard time is placed in the firstsymbol and the last symbol of the non-shifting subframe, but the guardtime may be placed only in the first symbol of the non-shiftingsubframe. In this case, the R-PUSCH may also be transmitted in the lastsymbol of the non-shifting subframe.

If the guard time is placed in the first symbol and the last symbolwithin the relay zone and the guard time is smaller than one symbol(e.g., the guard time is a ½ symbol), radio resources of a ½ symbolremain in each of the first symbol and the last symbol. In case of therelay station 1, radio resources 372 and 373 are combined, and thusradio resources of one symbol or more may remain in the time domain.

FIG. 38 shows radio resources remained in the first symbol and the lastsymbol of a non-shifting subframe if the guard time is placed in thefirst symbol and the last symbol. The guard time may be, for example, a½ symbol.

Referring to FIG. 38( a) and FIG. 38( b), the radio resources remainedin the first symbol and the last symbol may be combined to form onesymbol. FIG. 38( a) shows a case where an R-PUCCH is transmitted. Here,the combined symbol may be used for R-PUCCH or R-PUSCH transmission.FIG. 38( b) shows a case where an R-PUCCH is not transmitted. In thiscase, the combined symbol may be used for only R-PUSCH transmission.

FIG. 39 shows a subframe structure in which an R-PUCCH and an R-PUSCHare subjected to TDM if the guard time is placed in the first symbol andthe last symbol of a shifting subframe.

FIG. 39 is different from FIG. 37 in that the boundary of a symbol isforward shifted in the time domain of a relay zone. Accordingly, therelay zone may not be identical with a band in which a PUSCH istransmitted at the boundary for every symbol. Furthermore, the number ofsymbols included in the relay zone may be increased as compared withFIG. 37. For example, if each guard time is a ½ symbol in case of anormal CP, the relay zone may use 12 symbols in the time domain in FIG.37, but the relay zone may use 13 symbols in the time domain in FIG. 39.If a radio resource region 392 or 393 generated because a symbolboundary has moved is called a special resource region, the specialresource region may be used for R-PUSCH transmission. The method of FIG.39 is the same as the method described with reference to FIG. 37 exceptthe above difference.

FIG. 40 shows the special resource region if the guard time is placed inthe first symbol and the last symbol of a shifting subframe. The guardtime may be, for example, a ½ symbol.

FIG. 40( a) shows that an R-PUCCH and an R-PUSCH are transmitted in thenon-shifting subframe, and FIG. 40( b) shows that an R-PUCCH and anR-PUSCH are transmitted in the shifting subframe. As shown in FIG. 40(b), in the shifting subframe, points of time at which the R-PUCCH andthe R-PUSCH are transmitted are forward shifted, as compared with thenon-shifting subframe. Consequently, additional radio resources (i.e., aspecial resource region) are generated prior to guard time placed in thelast of the subframe. FIG. 40( c) and FIG. 40( d) show the non-shiftingsubframe and the shifting subframe in which the R-PUCCH is nottransmitted. Like in FIG. 40( b), in FIG. 40( d), a special resourceregion is generated. The special resource region may be used to transmitthe R-PUSCH or may be used for special purposes.

FIG. 41 shows a subframe structure in which an R-PUCCH and an R-PUSCHare subjected to TDM if the guard time is placed only in the firstsymbol of a shifting subframe.

The last symbol included in the relay zone may also be used because theguard time is placed only in the first symbol of the subframe. The relayzone is allocated to a specific frequency band between frequency bandsin which PUCCHs are transmitted. The R-PUCCH and the R-PUSCH aresubjected to TDM within the relay zone. The frequency bands may bedistinguished from each other and allocated within the relay zone forevery relay station. The R-PUCCH is not necessarily transmitted withinthe frequency band allocated to the relay station. For example, in FIG.41, in case of a relay station 1 RS#1, the R-PUCCH is not transmitted,but only the R-PUSCH is transmitted in the allocated frequency band. Incase of a relay station 2 RS#2, however, both the R-PUCCH and theR-PUSCH are transmitted in the allocated frequency band. If the R-PUCCHis not transmitted, relevant radio resources may be used to transmit theR-PUSCH. Alternatively, although the R-PUCCH is not actuallytransmitted, the relevant radio resources may remain for R-PUCCHtransmission. For example, the relevant radio resources may remain forACK/NACK transmission. Here, if a plurality of ACK/NACK has to betransmitted, radio resources may be subjected to CDM. A CCE index towhich the R-PUCCH is allocated may be determined by the CCE index of theR-PDCCH.

The R-PUSCH may use a smaller number of symbols than that of a PUSCHowing to the guard time and the symbol in which the R-PUCCH istransmitted in the time domain. The number of symbols used in theR-PUSCH may be set to a specific number in order to reduceimplementation complexity or a different number of symbols may be usedfor every relay station.

FIG. 41 is different from FIG. 39 in that the guard time is placed inthe start portion of the subframe in the relay zone. Accordingly, thereis an advantage in that a larger number of radio resources may be usedas compared with the method described with reference to FIG. 39.

If the guard time is placed only in the start position of the shiftingsubframe, but not placed in the end position thereof, a relay stationmay have a problem in receiving a signal from a relay UE at the startposition of a subsequent subframe in the shifting subframe.

FIG. 42 shows an operation of a relay station transmitting and receivingsignals in a series of shifting subframes in each of which the guardtime is placed only in a first ½ symbol.

The relay station transmits a signal to a BS in a subframe #2 andreceives a signal from a relay UE in a subframe #3. In this case, sincethe relay station cannot receive and decode a signal from the relay UEin a region 421 including the first ½ symbol of the subframe #3, accessuplink performance may be degraded. Accordingly, the relay UE maypuncture a symbol (i.e., the first ½ symbol of the subframe #3) on whichthe relay station cannot receive a signal and then transmit a signal ormay perform rate matching and then transmit a signal (e.g., in case ofan LTE-A UE). Alternatively, the relay UE may transmit a signal from thestart position of the subframe #3 irrespective of whether the relaystation can receive a signal (e.g., in case of the existing LTE UE). Therelay station may attempt to receive a signal, transmitted by theexisting LTE UE in the subframe #3, from the first symbol of thesubframe #3 for backward compatibility and may receive and decode asignal, transmitted by an LTE-A UE, from a point of time at which thefirst ½ symbol of the subframe #3 has elapsed.

A method of a relay station transmitting an R-SRS to a BS in thesubframe structure in which the R-PUCCH and the R-PUSCH are subjected toTDM, described with reference to FIGS. 37 to 42, is described below.

FIG. 43 shows an example in which an R-SRS is transmitted if the guardtime is placed in the first symbol and the last symbol of a non-shiftingsubframe.

The R-SRS may be transmitted in a band in which an R-PUSCH istransmitted in the frequency domain. The band in which the R-PUSCH istransmitted may be fixed or semi-statically allocated. The band in whichthe R-SRS is transmitted may be determined according to the band inwhich the R-PUSCH is transmitted. The band in which the R-SRS istransmitted does not overlap with the band in which an SRS istransmitted in the frequency band. The band in which the R-PUSCH istransmitted or the band in which the R-SRS is transmitted may beinformed through a higher layer signal, such as RRC signaling or may beinformed through a physical layer signal, such as a scheduling grant.

The R-SRS does not overlap with the SRS even in the time domain. Forexample, the R-SRS may be transmitted in the second symbol from the lastof a subframe in the time domain. If the R-SRS is transmitted in thesubframe, the number of symbols available for a relay station is reducedby 1. Accordingly, in the format of the R-PUSCH, one symbol may bepunctured or subjected to rate matching.

FIG. 44 shows another example in which an R-SRS is transmitted if theguard time is placed in the first symbol and the last symbol of anon-shifting subframe.

The R-SRS may be transmitted in bands other than bands in which PUCCHsare transmitted in the frequency band in which an SRS can betransmitted. The R-SRS is not necessarily transmitted in a bandidentical with the band in which the R-PUSCH is transmitted. Forexample, in FIG. 44, a band in which a relay station 2 RS#2 transmits anR-PUSCH is not identical with a band in which the relay station 2 RS#2transmits an R-SRS. That is, the R-SRS may overlap with the band inwhich the PUSCH is transmitted and then transmitted. In this case, thenumber of symbols available for the band in which the PUSCH istransmitted is reduced by 1. Accordingly, in the format of the PUSCH,one symbol may be punctured or subjected to rate matching. FIG. 44 isdifferent from FIG. 43 in the frequency band in which the R-SRS can betransmitted.

FIG. 45 shows yet another example in which an R-SRS is transmitted ifthe guard time is placed in the first symbol and the last symbol of anon-shifting subframe.

FIG. 45 is different from FIG. 44 in that a band in which the R-SRS istransmitted is the entire system band. In this case, a PUSCH or a PUCCHtransmitted by a macro UE may be influenced by the R-SRS. However, aninfluence on a wireless communication system is not great because theR-SRS is not frequently transmitted.

The method described with reference to FIGS. 43 to 45 may also beapplied to a case where the guard time is placed only in the firstsymbol of the non-shifting subframe. If the guard time is placed only inthe first symbol of the non-shifting subframe, the R-SRS is transmittedin the last symbol of the subframe.

FIG. 46 shows an example in which an R-SRS is transmitted if the guardtime is placed in the first symbol and the last symbol of a shiftingsubframe.

FIG. 46 is different from FIG. 43 in that symbols included in the relayzone are forward shifted. A symbol on which the R-SRS is transmitted maybe forward shifted by the guard time, as compared with a symbol on whichan SRS is transmitted.

For example, if each guard time of the first symbol and the last symbolis a ½ symbol, symbols included in the relay zone are forward shifted bythe ½ symbol. In case of a normal CP, the number of symbols included inthe relay zone is 13.

FIG. 47 shows an example in which an R-SRS is transmitted in the entiresystem band if the guard time is placed in the first symbol and the lastsymbol of a shifting subframe.

A PUSCH or a PUCCH transmitted by a macro UE may be influenced becausethe R-SRS is transmitted in the entire system band. If the R-SRS istransmitted, the PUCCH, the PUSCH, and the R-PUSCH have to have onesymbol punctured or subjected to rate matching. However, an influence ona wireless communication system is not great because the R-SRS is notfrequently transmitted.

FIG. 48 shows an example in which an R-SRS is transmitted if the guardtime is placed only in the first symbol of a shifting subframe.

Symbols included in the relay zone are more forward shifted than symbolsincluded in the band in which a PUSCH is transmitted. However, theboundary of a symbol in which the R-SRS is transmitted in the relay zoneis identical with the boundary of a symbol in which an SRS istransmitted. A frequency band in which the R-SRS is transmitted may belimited to the band in which the R-PUSCH is transmitted.

FIG. 49 shows another example in which an R-SRS is transmitted if theguard time is placed only in the first symbol of a shifting subframe.

FIG. 49 is different from FIG. 48 in that a frequency band in which theR-SRS can be transmitted includes bands other than bands in which PUCCHsare transmitted, from the entire system band. Accordingly, both theR-SRS and the SRS can be transmitted at the same time in some bands(e.g., the bands in which PUSCHs are transmitted).

FIG. 50 shows yet another example in which an R-SRS is transmitted ifthe guard time is placed only in the first symbol of a shiftingsubframe.

FIG. 50 is the same as FIG. 49 in that a frequency band in which theR-SRS can be transmitted includes bands other than bands in which PUCCHsare transmitted, from the entire system band. However, FIG. 50 isdifferent from FIG. 49 in that the R-SRS is multiplexed with the SRS andthen transmitted in the band in which the R-SRS may be transmitted. Themultiplexing method may use the ‘transmission comb’ method describedwith reference to FIG. 35. For example, the R-SRS and the SRS may bemultiplexed so that the R-SRS can be transmitted through a subcarrierhaving an even index and the SRS can be transmitted through a subcarrierhaving an odd index, and vice versa.

FIG. 51 shows still another example in which an R-SRS is transmitted ifthe guard time is placed only in the first symbol of a shiftingsubframe.

FIG. 51 is different from FIG. 49 in that a frequency band in which theR-SRS can be transmitted is the entire system band. The R-SRS may bemultiplexed with the SRS.

FIG. 52 shows further another example in which an R-SRS is transmittedif the guard time is placed only in the first symbol of a shiftingsubframe.

FIG. 52 is the same as FIG. 51 in that a frequency band in which theR-SRS can be transmitted is the entire system band. However, FIG. 52 isdifferent from FIG. 51 in that the R-SRS is multiplexed with the SRS andthen transmitted in the band in which the R-SRS can be transmitted. Themultiplexing method may use the ‘transmission comb’ method describedwith reference to FIG. 35.

FIG. 53 is a block diagram showing a wireless communication system inwhich the embodiments of the present invention are implemented. A BS 500includes a processor, 510, memory 530, and an RF (radio frequency) unit520. The processor 510 performs scheduling for allocating radioresources to a relay station and receiving a signal from a relaystation. In the above embodiments, the procedures, schemes, andfunctions performed by the BS may be implemented by the processor 510.The memory 530 is coupled to the processor 510 and configured to storevarious pieces of information for driving the processor 510. The RF unit520 is coupled to the processor 510 and configured to transmit orreceive or both a radio signal. The BS may become a source station or adestination station.

A relay station 600 includes a processor 610, memory 620, and an RF unit630. The processor 610 transmits R-PUCCHs and R-PUSCHs through radioresources allocated thereto. In the above embodiments, the procedures,schemes, and functions performed by the relay station may be implementedby the processor 610. The memory 620 is coupled to the processor 610 andconfigured to store various pieces of information for driving theprocessor 610. The RF unit 630 is coupled to the processor 610 andconfigured to transmit or receive or both a radio signal. The relaystation may become a source station or a destination station.

The processor 510, 610 may include ASICs (Application-SpecificIntegrated Circuits, other chipsets, logic circuits, and/or dataprocessors. The memory 530, 620 may include ROM (Read-Only Memory), RAM(Random Access Memory), flash memory, memory cards, storage media and/orother storage devices. The RF unit 520, 630 may include a basebandcircuit for processing a radio signal. When the above-describedembodiment is implemented in software, the above-described scheme may beimplemented using a module (process or function) which performs theabove function. The module may be stored in the memory 530, 620 andexecuted by the processor 510, 610. The memory 530, 620 may be placedinside or outside the processor 510, 610 and connected to the processor510, 610 using a variety of well-known means.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

Although the some embodiments of the present invention have beendescribed above, a person having ordinary skill in the art willappreciate that the present invention may be modified and changed invarious ways without departing from the technical spirit and scope ofthe present invention. Accordingly, the present invention is not limitedto the embodiments and the present invention may be said to include allembodiments within the scope of the claims below.

1. A method of a relay station transmitting a signal in a wirelesscommunication system, the method comprising the steps of: placing guardtime within at least one symbol period in a subframe including aplurality of symbol periods in a time domain; and transmitting a controlsignal or data to a base station using symbol periods other than thesymbol period, including the guard time, in the subframe, wherein theguard time is equal to or shorter than one symbol period, and astructure in which the control signal or the data is placed in each ofthe symbol periods of the subframe is determined based on a number ofsymbol periods other than the symbol period including the guard time. 2.The method as claimed in claim 1, wherein the guard time is placed in afirst symbol period of the subframe.
 3. The method as claimed in claim2, further comprising: transmitting a relay sound reference signal(R-SRS) in the subframe, wherein a symbol period in which the R-SRS istransmitted is a last symbol period of the subframe.
 4. The method asclaimed in claim 3, wherein the R-SRS is transmitted only in a frequencyband in which the data is transmitted or a frequency band in which thecontrol signal and the data are transmitted.
 5. The method as claimed inclaim 3, wherein the R-SRS is multiplexed with an SRS transmitted frommacro user equipment to the base station and then transmitted.
 6. Themethod as claimed in claim 5, wherein the multiplexing includesallocating different subcarriers to the R-SRS and the SRS.
 7. The methodas claimed in claim 5, wherein the R-SRS is transmitted in an entiresystem band.
 8. The method as claimed in claim 1, wherein the guard timeis placed in a first symbol period and a last symbol period of thesubframe.
 9. The method as claimed in claim 8, wherein each of guardtime placed in the first symbol period and guard time placed in the lastsymbol period is a ½ symbol period.
 10. The method as claimed in claim8, wherein a resource block allocated to transmit the control signal isdifferent from a resource block allocated to a control signaltransmitted from user equipment to the base station.
 11. The method asclaimed in claim 8, wherein reference signals or payloads in a frequencyband in which the control signal is transmitted are placed in symbolperiods symmetrical to each other based on a boundary of slots of thesubframe.
 12. The method as claimed in claim 11, wherein an identicalorthogonal sequence is applied to the payloads placed in the symbolperiods symmetrical to each other based on the slot boundary, from amongthe payloads.
 13. The method as claimed in claim 8, further comprising:transmitting an R-SRS using any one of symbol periods not including theguard time in the subframe, wherein a symbol period in which the R-SRSis transmitted is not identical with a symbol period in which macro userequipment transmits an SRS to the base station.
 14. The method asclaimed in claim 13, wherein the R-SRS is transmitted through a secondsymbol period from the last symbol period of the subframe.
 15. Themethod as claimed in claim 1, wherein a boundary of symbol periods in afrequency band in which the control signal or the data is transmitted isshifted by the guard time from a boundary of symbol periods in afrequency band in which user equipment transmits a control signal ordata to the base station.
 16. The method as claimed in claim 1, whereinthe relay station transmits the control signal and the data in anidentical frequency band, but transmits the control signal and the databy performing TDM (Time Division Multiplexing) for the control signaland the data in a time domain.
 17. A signal transmission apparatus of arelay station, comprising: a radio frequency unit configured to transmitand receive a radio signal; and a processor coupled to the radiofrequency unit, wherein the processor places guard time within at leastone symbol period in a subframe including a plurality of symbol periodsin a time domain and transmits a control signal or data to a basestation using symbol periods other than the symbol period, including theguard time, in the subframe, wherein the guard time is equal to orshorter than one symbol period, and a structure in which the controlsignal or the data is placed in each of the symbol periods of thesubframe is determined based on a number of symbol periods other thanthe symbol period including the guard time.